Intermittent starting fault with e34 520i

[dwaynos]

Hi, Yesterday i was out driving and the car stopped. The engine was just turing and turning but would not fire. i gave it a minute then it fired up again. I replaced the fuel filter earlier and ran it until it stopped. When it stopped i removed the supply pipe from the fuel lift pump and switched the ignition on. i did not get any fuel coming from it with the ignition on. I beleive the fault could be with the fuel lift pump, some dodgy wiring going to the pump or the immobiliser. What do you guys think?

Thanks

[whiskychaser]

Hi, Yesterday i was out driving and the car stopped. The engine was just turing and turning but would not fire. i gave it a minute then it fired up again. I replaced the fuel filter earlier and ran it until it stopped. When it stopped i removed the supply pipe from the fuel lift pump and switched the ignition on. i did not get any fuel coming from it with the ignition on. I beleive the fault could be with the fuel lift pump, some dodgy wiring going to the pump or the immobiliser. What do you guys think?

Thanks
The pump only runs when the engine is being cranked or it is actually running. Jumpering the fuel pump relay pins 30 & 87 will run the pump while you do your checks

[dwaynos]

i dont know because i checked it when the car was working. i removed the pipe, swithed the ignition on and fuel came out.

[whiskychaser]

When it stopped i removed the supply pipe from the fuel lift pump and switched the ignition on. i did not get any fuel
or:
i removed the pipe, swithed the ignition on and fuel came out.

Cant be both. Or as Terry Wogan would say, 'Is it me?

[dwaynos]

no what i mean is when the car decides to start i will switch it off and remove the pipe then switch the ignition on and fuel will come out. if the car does not want to start and it is just turning over and i remove the pipe then switch on the ignition no fuel will come out. could it be a dodgy fuel pump or an immobiliser problem?

[whiskychaser]

no what i mean is when the car decides to start i will switch it off and remove the pipe then switch the ignition on and fuel will come out. if the car does not want to start and it is just turning over and i remove the pipe then switch on the ignition no fuel will come out. could it be a dodgy fuel pump or an immobiliser problem?
Think I'm with you now-basically there is no fuel in the pipe when the engine wont start. So its either a duff pump or the circuit supplying it?
I'd jumper the relay to eliminate that first. Then check the voltage and ground at the pump. (IIRC there is a fuse between the relay and the pump so check that too).

[tim eh?]

There is an electrical plug near the fuel pump that can get corroded, might be worth a check. It's just inside the fuel tank access plate in the trunk.

[dwaynos]

yes thats right. i dont know where the fuel pump relay is and which one it is. also how do i jumper the relay? and can i leave it like that for a good amount of time just to make sure its not going to stop when im out driving?

thanks for the replies

[whiskychaser]

yes thats right. i dont know where the fuel pump relay is and which one it is. also how do i jumper the relay? and can i leave it like that for a good amount of time just to make sure its not going to stop when im out driving?

thanks for the replies
The fuel pump relay is the middle one of the 3 in the e-box. If you pull the relay out you will see the number next to each pin. Connect the 'holes' in the socket that correspond to pins 30 & 87. I've used a split pin but to be safe you should use a piece of wire with an in-line fuse. I think the pump will run whether you have the ignition on or not so I dont believe its safe to drive any distance like that.

Edit: What you could do is connect a fine wire with an LED in line to ground and the other end to whichever of pin 30 or 87 is not the perm. live and put the relay back in. That way you will get an indication if the relay stops working for some reason. HTH

[dwaynos]

The fuel pump relay is the middle one of the 3 in the e-box. If you pull the relay out you will see the number next to each pin. Connect the 'holes' in the socket that correspond to pins 30 & 87. I've used a split pin but to be safe you should use a piece of wire with an in-line fuse. I think the pump will run whether you have the ignition on or not so I dont believe its safe to drive any distance like that.

Edit: What you could do is connect a fine wire with an LED in line to ground and the other end to whichever of pin 30 or 87 is not the perm. live and put the relay back in. That way you will get an indication if the relay stops working for some reason. HTH

The LED idea sounds good to me. So do i put the cathode of the led to a point on the chassis? What do you mean when you say 30 or 87 is not the perm. live? Also is the e-box under the bonnet?

Thanks

[whiskychaser]

The LED idea sounds good to me. So do i put the cathode of the led to a point on the chassis? What do you mean when you say 30 or 87 is not the perm. live? Also is the e-box under the bonnet?

Thanks
Yes the e-box is under the bonnet on the right hand wing next to the bulkhead. The lid is held on by 4 x-head screws. I'd use a 12V LED with a built in resistor and yes connect the cathode (the shorter lead) to ground.
If you connect your anode wire to pin 30 or pin 87, one will make it light up. Connect it to the the one that doesnt-it should only be lit when the engine is cranked or running. Bear in mind that a bad crank sensor will not give the signal to 'turn on' the relay.